基于枝节加载技术的宽带分支线耦合器

Broadband Branch-line Coupler Based On Stub-loading Technique

摘要:

针对当前通信系统对宽频带和高平坦度耦合器的需求,设计了一款基于枝节加载技术新型宽带分支线耦合器。在对耦合器奇偶模分析过程中将奇偶模模型视为枝节滤波器,在模型端口引入半波长微带线,显著提高了奇偶模模型的带宽和平坦度。将该优化方案代入耦合器本体,有效提升了耦合器的带宽。同时为了控制耦合器的尺寸,采用枝节加载技术等效替换耦合器微带线与加载线,在提升耦合器带宽的前提下有效控制了耦合器的尺寸,在此基础上通过弯曲传输线保证电路结构的紧凑进一步控制耦合器尺寸。通过电磁仿真软件进行优化设计,所得的耦合器在2.58GHz-3.12GHz带宽内平坦度低于0.4dB,回波损耗大于20dB,带内耦合端口与直通端口的输出信号幅度差异不超过0.34dB,且相位差处于90°±2°之间。耦合器尺寸22.64mm*19.63mm(约为),对所设计的耦合器进行实物加工测试,测试结果与设计仿真结果较为贴近,证明了设计的有效性。

Abstract:

In response to the current communication systems" need for wide bandwidth and high flatness couplers, this paper presents a new wideband branch-line coupler based on stub-loading technology. During the even-odd mode analysis, the even-odd mode model is treated as a stub filter. A half-wavelength microstrip line is introduced at the model ports, significantly improving the bandwidth and flatness of the even-odd mode model. This optimization scheme is then applied to the coupler body, effectively enhancing the bandwidth.To control the size of the coupler, stub-loaded technology is used to equivalently replace the microstrip line and the loading line of the coupler. This method effectively controls the size while improving the bandwidth. Additionally, using bent transmission lines ensures a compact circuit structure, further controlling the size of the coupler. Through optimization using electromagnetic simulation software, the resulting coupler achieves a flatness of less than 0.4dB within the bandwidth of 2.58GHz to 3.12GHz and a return loss greater than 20dB. The amplitude difference between the output signals of the coupling port and the through port does not exceed 0.34dB, with a phase difference within 90°±2°. The coupler measures 22.64mm*19.63mm (approximately 0.5λ*0.5λ). The fabricated coupler was tested, and the results closely match the simulations, proving the effectiveness of the design.